The invention relates to a magnetic sensor comprising a generally flat and elongate magneto-resistance element which at two oppositely located ends has contacts for the connection to a source of measuring current, which element shows a magnetic anisotropy in which the easy axis of magnetization lies in the major plane of the element, the sensor further comprising two magnetically permeable components situated in one plane between which components a gap is present which gap is bridged magnetically by the magneto-resistance element, the sensor furthermore comprising a body of magnetically permeable material disposed parallel to the two components, the body having one end coupled magnetically to an end of a first of the two components remote from the gap, an end of the second of the magnetically permeable components remote from the gap being adapted to be brought in a flux coupling relationship with an external magnetic field.
The invention relates, in particular to magnetic sensors which may be used to detect magnetic fields of magnetic recording media, for example, magnetic tapes or disks.
A geometric arrangement of a magneto-resistance element bridging a gap between two magnetically permeable elements is known from U.S. Pat. No. 3,921,217. In itself, a magneto-resistance element may be of the magnetically biased type in which it is necessary, for linearizing the playback characteristic of the magneto-resistance element, to apply a static magnetic field so as to move the operating point to a linear region of the resistance-magnetic field curve, or it may be a current-biased type magneto-resistance element. This current-biased type is a magneto-resistance element in which one or more inclined and electrically readily conductive strips are provided on one of the element surfaces at an angle of approximately 45.degree. with the longitudinal axis of the element. These strips serve as equipotential strips so that the direction of the current in the element which is at right angles to the equipotential strips encloses an angle of also approximately 45.degree. with the easy axis of magnetization. In this manner, the transmission characteristic is linearized.
In a sensor of the above-described type having two magnetically permeable components separated by a gap (so-called flux conductors) which together with a further magnetically permeable element or return limb form a partially open magnetic circuit, the free (second) magnetically permeable component as it were "sucks" the flux of a presented magnetic field and couples it to the magneto-resistance element, after which the flux is returned via the first magnetically permeable component and the magnetically permeable element.
For a high sensitivity, that is to say for an optimum coupling of the presented flux from one flux conductor to the magneto-resistance element and, thence, to the other flux conductor, it is important that the distance between the magneto-resistance element and the flux conductors should be kept as small as possible.
As said distance becomes smaller, the noise in the output signal of the magneto-resistance element, however, increases as does the harmonic distortion. When said distance is increased, noise and distortion decrease but the sensitivity also decreases.